High pressure contact air-break switch



.Aug. 18, 1942. 1-. F. JOHNSON 2,293,552

men PRESSURE cormc'r AIR-BREAK swrrcn Filed Aug. 16, 1941 Patented Aug. 18, 1942 UNITED STATES PATENT OFFICE HIGH PRESSURE CONTACT AIR-BREAK SWITCH Claims.

This invention relates to high tension, airbreak switches and, among other objects, aims to provide a greatly improved high pressure contact for use in switches capable of carrying heavy currents. The idea is to employ greater contact pressure which can be distributed over less area than is ordinarily required for the usual low pressure contacts. Another .important aim is to provide a cam contact member acting in conjunction with a retractable blade switch, wherein a movable cam member coacts with the blade during its final closing movement to make a high pressure contact when the operating mechanism has its greatest mechanical advantage. Still another aim is t provide in a switch of this type means to vary the contact pressure by making a simple adjustment,

Other aims and advantages of the invention will appear in the specification, when considered in connection with the accompanying drawing,

wherein:

Fig. 1 is a side elevation showing a single pole switch embodying the invention, the contact member being practically broken away and shown in section;

Fig. 2 is a fragmentary side elevation partly in section showing the blade and contact member in a different position from that in Fig. l; and

Fig. 3 is an end elevation showing the contact 1 member and associated parts.

Referring particularly to the drawing, the improvements are shown as being applied to a retractable blade switch having operating mechanism like that shown in my Patent No. 2,248,876. However, it is to be understood that the contact is applicable to other types of switches wherein the switch blade has compound opening and closing movements. In this instance, the switch is mounted on a stationary insulator l0 and is adapted to be operated by a rotatable insulator I I. The blade is carried by a bracket l2 pivotally mounted on pairs of parallel links l3 and M which are connected to each other by a link [5. The rear pair of links is jointed or articulated to permit the blade to swing to an upright position after it is moved horizontally to its circuit breaking position, It is connected to be operated by a crank I 6 mounted on the insulator H and having a double-jointed link ll pivotally connected to an ear IS on the forward portion of the bracket I2 ahead of the parallel linkage as clearly described in the aforesaid patent.

The switch blade is here shown as being forked shaped and comprises a pair of strap metal spring blade members l9 and bolted at their rear ends to the forward end of the supporting bracket or arm I2. They are preferably connected intermediate their ends by a spacer member 2|. The lower blade member [9 is somewhat shorter than the upper blade member and the inner faces of both of them have metal contact pads 22 and 23 which cooperate with a rocking contact cam 24 carried on a pair of pivoted arms 25 mounted between upstanding ears 25 on a shaft 2'! carried by a stationary insulator 23. The rocker arms and cam member are here shown as being inverted U-shaped and the upper and lower faces 26 and 30 of the contact member 24 are arcuate in cross section so that the cam is the segment of a cylinder, with the upper face being of somewhat greater area than the lower face. The contact pads or tips 22 and 23 are likewise shown as being curved to conform to the curved contact surfaces of the contact cam so that, when the blade is moved to the position shown in Fig. l, the curved surfaces make contacts of substantial areas.

The front of the lower blade member is is shown as having its side edges bevelled so as to be guided between the arms 26. When the switch blade swings from the position, the lower blade member extends beyond the rocker arms as shown in Fig. 1.

To provide for varying the contact pressure, the blade members [9 and 26 are shown as having spring leaves 3! and 32 anchored at their rear ends by bolts and rivets 33 and having their free ends resting upon protuberances 34 similar to rivet heads. A bolt 35 extends through the leaves and the blade members and has a compression spring 36 adapted to be compressed by a nut 31. A spacer sleeve 38 limits the closing movement of the spring ends of the blade members.

The rocker cam is limited in its rearward pivotal or swinging movement by stop members 39 on the supporting plate 40 which cooperates with lugs or ears 4| on the arms 25. Also the arms are normally biased to the position shown in Fig. 2 by coil springs 42 connected to the supporting plate and the arms. In this normal inactive position the cam contact is initially engaged by the forked blade. The arms also have integral contact pads 43 to which are connected ordinary flexible conductors 44 leading to the main conductor terminal 45 In the operation of the switch, it will be seen that the link operating mechanism has swung the blade to its horizontal position as shown in Fig. 2 and the forked open end of the blade has straddled the cam having been advanced forwardly toward switch closing position. It will be noted that the cam, when in that position, is narrower than the gap or space between the contact pads. As the blade advances toward closed position, the contact pads on the blade members [9 and 20 force or push the rocker arms 25 toward the position shown in Fig. 1 by their engagement with the cam contact member 24. When the rocker arms reach the final switch closing position, the cam has been turned or moved to its transverse position between the pads in the forked end of the blade with its convex contact surfaces fully engaging the concave contact surfaces of the pads, thus expanding the fork against the inherent spring tension of the blade arms and the compression of the coil spring 36. The pressure can be very great because of the great mechanical advantage derived from the operating mechanism. The crank l6 approaches its dead center during the final closing movement of the blade and slows up its action while increasing the force or mechanical advantage until it reaches the dead center. Thus, no extra manual effort is required to close the switch. During the opening movement the blade is retracted substantially horizontally until the fork disengages the cam, and the blade is then swung in an arcuate path by the actuating mechanism, shown, the blade will swing through slightly more than 90 to a stable open position in which the weight of the whole blade rests upon the rear compound link.

The switch is so disposed that when gangoperated, each pole reaches its maximum pressure on its contact cam practically at the time that the fork begins to rock the cam. From then on, the rotation of the cam does not increase the pressure, but affords over-travel of the blade; so that, if there is any difference in the relative longitudinal positions of the blades of the usual three poles, this will allow any of them to advance far enough to permit even the hindermost blade to develop full pressure on the cam contact. This will counteract considerable error in installing and adjusting multi-pole switches; that is to say, all of the switch contacts will close under the same pressure, regardless of the fact that one blade may be behind or ahead of another during the closing movement. From the foregoing description, it will be seen that the switch is relatively simple in its design and the contact is very effective to conduct heavy currents up to several thousand amperes. It has a small contact area and is easily manipulated by ordinary operating mechanism. It is of less weight per unit of current capacity and can be manufactured at lower cost than an ordinary, low pressure contact switch with a relatively large contact area or any ordinary, high pressure point or line contact switch designed to carry the same current. 7

Obviously, the present invention is not restricted to the particular embodiment thereof herein shown and described. Moreover, it is not indispensable that all the features of the invention be used conjointly, since they may be used advantageously in various combinations and subcombinations.

If the switch is horizontal as What is claimed is:

1. A high tension, air-break switch of the character described comprising, in combination, a retractable, and swinging blade having a spring fork composed of strap metal members; crank means to operate the blade; contact pads in the fork having concave, arcuate faces; a rocking cam contact having convex faces engageable with the arcuate faces of said contact pads when the blade approaches its closed position to rock the cam into high pressure contact with the contact pads; and spring means connected to bias the rocking contact member into position to be engaged by the fork.

2. A high tension, air-break switch of the character described comprising, in combination, a retractable blade having a spring fork at its contact end composed of strap metal members; means to operate the blade and impart compound rectilinear and swinging movement thereto; spacer means between the fork members; pivoted arms carrying a cam-shaped contact member adapted to be engaged by the blade fork and rocked into high pressure cam engagement therewith as the blade approaches its closed position; tension springs connected to the contact arms to bias it to its normal position when the switch blade is open; and stop means to limit the swinging movement of said arm.

3. In a high tension, air-break switch of the character described, a retractable blade having a spring fork at its contact end; contact pads in the end of the spring fork having concave contact faces; a rocking cam-shaped contact member having convex contact surfaces to coact with the concave faces of the contact pads and adapted to be engaged by the contact pads to rock the contact member into circuit closing position to make high pressure contact between the cam and the contact pads; and means to return the rocking cam to its initial position when the switch blade is moved to its open position.

4. A high tension, air-break switch of the character described comprising, in combination, a retractable blade having a spring fork at its contact end; a spacer member between the fork members; a bolt extending through the fork members and carrying a compression spring acting thereon, whereby the spring pressure may be varied; a rocking cam contact member adapted to be straddled and engaged by the fork to be rocked into circuit closing position and thereby make high pressure contact with the fork; and spring means connected to the contact member to return it to its initial position to be engaged by the blade.

5. A high tension air-break switch of the character described comprising, in combination, a blade having a spring fork at its contact end; compound links pivotally connected to the blade and having provision for both retracting and swinging movement of the blade; and a pivotally mounted contact arm carrying a cam-shaped contact member coacting with the forked end of the blade and so arranged that when the'blade is retracted, it will be constrained to move substantially parallel to itself by said contact arm and said contact links.

TOMLINSON F. JOHNSON. 

